The present invention relates to an insulated gate type semiconductor device having a protection element, and a method of manufacturing the device. Especially, the invention relates to an insulated gate semiconductor device which is suitable for forming a trench type insulated gate semiconductor element with a lateral type insulated gate semiconductor element or a polycrystalline silicon diode concerning an operation of the trench type insulated gate semiconductor element of in an identical chip, and a method of manufacturing the device.
For example, power MOSFET(Metal Oxide Semiconductor Field Effect Transistor) and IGBT (Insulated Gate Bipolar Transistor) are known as insulated gate type semiconductor elements. For improving a reliability and an added -value of the power MOSFET and the IGBT and for reducing a cost and a size of these semiconductor elements, in a case of forming these elements of power devices in a semiconductor substrate, an insulated gate type semiconductor device having a protection element such as a MOSFET with the power MOSFET and the IGBT in an identical chip is proposed. For example, a temperature detection circuit with a lateral type MOSFET and a polycrystalline silicon diode is formed in a drain region of a power MOSFET, using the manufacturing process of the planar type power MOSFET, as described in the Japanese Patent laid-open No. 63-229758. The temperature detection circuit turns off the power MOSFET, when the temperature of semiconductor chip is overheated over a pre-determined temperature.
The Japanese Patent laid-open discloses a polycrystalline silicon diode for preventing an electrostatic destruction between a gate and a source of a planar type power MOSFET in a chip of the planar type power MOSFET.
The trench type power MOSFET is proposed as an insulated gate type semiconductor element different from the planar type power MOSFET. In the trench type power MOSFET, a groove (trench) is formed in a semiconductor layer, and then a gate layer is formed in the groove through a gate oxide film, for reducing a power loss of the element. In addition, a channel width per unit area is lengthened by forming a channel in a side surface of the groove. In producing the trench type power MOSFET, a method of forming the groove after forming a source diffusion layer and a body (channel) diffusion layer is proposed, as described in the U.S. Pat. No. 5,298,442. On the other hand, a method of forming the source diffusion layer and the body (channel) diffusion layer after forming the groove is proposed, as described in Japanese Patent laid-open No. 4-17371. The former of these method is mainly adopted in general.
A method of forming the trench type power MOSFET and a FET protecting the power MOSFET on an identical chip is studied in Japanese Patent laid-open No. 9-82954. As the result, the method of using a gate buried in the trench as a gate of the FET protecting the trench type power MOSFET is proposed.